Treated Timber

Understanding Treated Timber

Treated Timber, often referred to as green treated or tanalised timber, undergoes a high-pressure preservative treatment process. This involves placing the wood in a vacuum chamber where chemical preservatives are forced deep into the timber’s cellular structure. This treatment is essential for wood that will be exposed to moisture or in direct contact with the ground, as it significantly extends the service life compared to untreated sawn timber.

The range consists of sawn-surfaced material, which maintains a slightly coarse texture ideal for structural applications where grip and mechanical bonding are more important than a smooth decorative finish. Because the treatment penetrates the outer layers of the wood, any cuts or notches made during installation must be re-treated with a suitable end-grain preservative to maintain the integrity of the protection.

These timber sections are predominantly used for "out of ground" applications such as joists, rafters, and studwork. The structural reliability of the timber ensures it can support significant loads while resisting the degradative effects of dampness often found in roof voids, floor spans, and external wall frames.

Material Range

• Roof Battens: Specifically sized timber strips used to support tiles and slates, featuring both ungraded and graded solutions such as Blue Graded Roof Battens.
• Structural Scantlings: A comprehensive range of sawn treated sections for framing and joists, including popular dimensions such as 2x2, 3x2, and 4x2.
• Large Format Joists: Heavy-duty treated sections designed for substantial spans and floor loads, featuring 6x2 and 8x2 profiles.
• Small Section & Wide Boards: Versatile treated timber available in smaller 2x1 profiles for non-structural use, alongside 6x1 and 8x1 boards.
  
  

Performance Benefits

• Biological Resistance: Chemically enhanced to resist wood-boring insects and fungal decay, ensuring long-term structural stability.
• Enhanced Longevity: Significantly outperforms untreated timber in external or humid conditions, reducing maintenance and replacement cycles.
• Versatility: Sawn finish provides an excellent surface for various fixings and is suitable for a wide array of construction and agricultural uses.
  
  

Typical Applications

• Roof Carcassing: Installation of rafters, purlins, and battens to create a rot-resistant roof structure.
• Floor Joists: Creating stable, decay-resistant bases for ground floor and upper floor constructions.
• Timber Framing: Constructing the primary internal and external stud walls for residential and commercial buildings.
• Garden Structures: Building the framework for decking, pergolas, and heavy-duty fencing.
  
  

Specification & Standards

• BS EN 335: Defines the use classes for wood-based products based on the risk of biological attack.
• BS 8417: The British Standard for the preservation of wood, providing recommendations for the treatment of timber.
• BS EN 14081: Requirements for strength-graded structural timber with rectangular cross-sections.
  
  

Related Materials and Construction Uses

Treated Timber is typically utilised as the primary skeleton of a build, working in conjunction with breathable membranes to protect the building envelope from water ingress. When used in roofing, it provides the necessary anchorage for slate or tile fixings, and in flooring, it serves as the support structure for moisture-resistant chipboard or plywood decking.

Depending on the load-bearing requirements of your project, you may require specific strength grades. While our range includes ungraded options for general-purpose use, we also provide professionally graded C16 Timber for standard structural applications and C24 Timber for projects requiring higher load capacities and wider spans. It is vital to use corrosion-resistant fixings, such as galvanised or stainless steel nails and screws, as the chemicals used in the pressure-treatment process can react with standard bright steel.